Main controls for a vehicle gasoline engine include an ignition control and an injector control.
During a control process, a control unit locates controlled parameter maps according to basic control conditions, corrects them based on the engine conditions reflected by a plural of sensors, outputs them to control a plural of actuators, and thus controls targets. The controls are open-loop controls and closed-loop controls.
An open-loop control of engine ignition timing is mainly based on an engine load signal which is determined by an intake flowrate signal and a throttle valve signal, an engine rotational speed signal and a crankshaft position signal. A closed-loop control of engine ignition timing is, based on feedback signals of knock sensor(s), to adjust an ignition system.
An open-loop control of an injector mainly detects the intake flowrate, calculates the injection time on the basis of the intake flowrate signal and other sensor signals upon different working status, and determines the quantity of gasoline injection, which, in fact, is the control of an air-fuel ratio. An closed-loop control of an injector measures the air-fuel ratio density of a gas mixture in the firebox of the engine based on oxygen content in the exhaust detected by an oxygen sensor. The closed-loop control further gets an error signal after the measured air-fuel ratio density signal is fed back to Engine Control Unit (ECU) and compared with the predetermined target air-fuel ratio, determines an injection pulse width, and keeps the air-fuel ratio near the predetermined target value. Currently, the air-fuel ratio is mostly maintained in a very narrow range near the theoretical air-fuel ratio of 14.7, which, at the sacrifice of partial economical efficiency and partial power characteristics, is to meet the exhaustion requirements for vehicles by employing a three-way catalyst device. In most working status (e.g. engine starting, warm-up, idle, heavy load, acceleration-deceleration), it is necessary to release from the closed-loop controls and enter into the open-loop controls.
Other engine controls include an idle control, an EGR control (exhaust gas recirculation system), an intake control, and others. The intake control is composed of a VTEC control (Variable Valve Timing and Lift Electronic Control System), a turbo charge control, a variable intake pipe length and variable intake manifold length control, a resonator intake inertia control, and others.
The engine idle control is an intake closed-loop control. The exhaust gas recirculation (EGR) control is an open-loop control, the control parameters of which include engine water temperature, intake gas temperature, rotational speed and throttle valve opening. In the intake control, the VTEC control is a mechanical control system, the function of which is to change a fixed valve stroke into a variable valve stroke in correspondence to the rotational speed of the engine. The turbo charge control controls variable intake sections. The variable intake pipe length and variable intake manifold length control and the resonator intake inertia control are pressure-wave inertia supercharging controls utilizing the intake pressure wave characteristic.
The control methods mentioned above are well applicable to the gasoline engine. However, the existing parameter maps control strategies are ineffective in dealing with the following problems:
(1) decreased control accuracy because of manufacture deviation associated with sensors and executable devices, variations in working characteristics due to abrasion and aging after a period of usage, matching deviation due to fittings replacements, and others;
(2) varied loads because of environment and season changes, working mediums changes (such as a machine oil viscosity change), electric appliances and auxiliary power access changes, and different operation of the engine;
(3) deviated measurements caused by measuring instruments and operating means used in optimizing the control unit on an engine testing bench, and other uncertain factors that are unconsidered;
(4) deviated real-time controls caused by signal transfer time lag of the sensors, operation process time lag of the control unit, movement time lag of the executable devices, and others.
The aforementioned problems affect the controlled targets resulting in deviation from the testing bench optimizations for the basic ignition parameter maps, the basic injection parameter maps and other controlled parameter maps. However, due to various time lag effects, one can only partially correct control deviation in correspondence to various condition signals fed back by the sensors, but cannot achieve a complete correction. Consequently, the engine is not able to operate efficiently.